This invention relates to a novel method and apparatus for producing composite nonwoven fiber webs or mats, and more particularly to an improved method and apparatus which permits the inexpensive production of substantially shingle-free nonwoven webs. Still further, this invention relates to a method of employing adjustable, web forming apparatus of the type described to produce composite nonwoven web structures of optionally different shapes and plies.
A major disadvantage of prior, known apparatus for producing nonwoven webs has been the tendency of the apparatus to produce a product which exhibits undesirable shingling. Typically, fibers are deposited at a first location on the operating surface of a rotating condenser or screen conveyor, which travels continuously in one direction. The deposited fibers form on the operating surface a nonwoven web or layer of fibrous material which is continuously doffed or removed from the surface at a second location downstream from the first location. The term "shingling" relates to the tendency of the deposited fibers to become angularly oriented in much the same direction, which causes the web structure to become weak because of less entanglement of its fibers.
As noted in greater detail hereinafter, the present invention permits the nonwoven fibers to form isotropically, or with no particular orientation, thus resulting in substantially greater entanglement of individual fibers in the web structure. The result is a web structure that has the same tear strength characteristics both in the machine direction (MD) of web formation, and in the cross machine direction (XD).
While many such prior apparatus of the type described have been capable of producing nonwoven webs or mats in continuous, multi-ply lengths, and also have been capable of incorporating resins in the webs or mats, such apparatus heretofore have not been capable of forming composite nonwoven structures of optionally different shapes and plies.
Accordingly, it is an object of the invention to provide improved nonwoven web forming apparatus which substantially eliminates any undesirable shingling in the webs or mats produced thereby.
Another object of this invention is to provide improved web forming apparatus of the type described which can be readily adjusted to produce composite nonwoven structures of various configurations, and of various plies within a given structure.
A further object of this invention is to provide a novel method of producing composite nonwoven structures or products of various configurations, and of various thicknesses or plies within a given structure.
Other objects of the invention will be apparent hereinafter from the specification and from the recital of the appended claims, particularly when read in conjunction with the accompanying drawings.